Answer: photon.
- A photon
- B electron
- C proton
- D neutron
Correct answer: A. photon
Explanation: Light energy comes in discrete packets called photons.
In the photoelectric setup, light striking the metal plate ejects electrons that cross the evacuated tube to the collector, producing a measurable current on the ammeter.
Concept context
Photoelectric effect, de Broglie waves, Bohr's model, atomic spectra.